Alert the user when is offline

Considering that the user needs to have a network connection to perform the tasks on the platform, there should be a very clear visual clue off the connection was lost, when it happens.

Message to present:
(aligned left) Your network in unavailable. Please check your connection.

Styling:
Should follow in general the same style from the class "toolbar" (applied to the div selectionToolbar) except:
background: #FEE066;
color: var(--nuxeo-text-default)

Expected Behavior
If Offline for >= 3'seconds, the bar should slide down from the top & when connection is restored, it should simply disappear.
Always visible if offline, to give a clear view to the user, of its real state and limitations.